The least expensive method of transporting large relatively constant quantities of liquids, slurries and gases is through pipelines buried in the earth. Once pipelines are built, operating costs are very small relative to the value of the contents being transported, safety concerns are much reduced and environmental impact from spills and leaks are very small. In other words, pipelines are the preferred method of transporting large quantities of liquids, slurries and gases. Unfortunately, initial capital costs are a very large proportion of the total cost of transporting fluids by pipeline meaning that very large sums are spent before any income is received. Accordingly, there is a large incentive to find less expensive techniques for installing or laying small and large diameter pipelines.
Laying pipelines in relatively flat or moderately hilly country is done routinely and is not exorbitantly expensive. Pipelining in mountains or other steeply inclined terrain is difficult and exorbitantly expensive. The standard technique for laying pipeline on a steeply inclined area such as a mountain side or across a fault scarp, is to trench the route on the steepest and most direct route and then lay pipe from the bottom upwardly toward the top. Pipe joints are welded together, one joint at a time, in the ditch. After the welds are inspected and the bared ends field coated, the ditch is backfilled by pushing spoil back in the ditch.
Installing pipelines on a steep incline is very slow, very dangerous and thus very expensive. There is always a danger of rocks, debris or equipment careening down the right-of-way, imperiling those below. It is difficult to stand on a steep incline, much less walk, weld or hold massive pipe joints in a position where they can be welded. There are many variables, of course, but it would not be surprising to learn that the cost per foot of laying pipe on a steep incline on any particular job may exceed $1000 per foot or be twenty five to thirty five times the cost per foot of laying comparable pipe in a conventional manner on flat ground or along a moderately hilly route where pipelining can be done in a normal manner.
A moderately sized spread of men and equipment can lay pipe on flat or moderately hilly ground at a surprisingly rapid rate. A common speed would be several miles per day of pipe welded together, field coated, inspected, transferred to the ditch and backfilled. In contrast, pipelining on a steep slope is very slow. A common speed would be one to two lengths of pipe per day, totalling perhaps eighty feet per day but it could be much slower depending on the steepness of the slope, the material on the surface, the weather, and the diameter of the pipe being installed.
Disclosures of interest relative to this invention are found in U.S. Pat. Nos. 2,991,974; 3,248,884; 5,197,713; 6,450,736 and 6,588,984.